Oil and petroleum products are stored and transported around the world for use in a variety of applications. Enormous pipelines and sea-going supertankers transfer millions of gallons of oil across the world, and one hazard of such large scale operations is the risk that oil or oil products will be spilled in or near water. As a result, containment and clean up measures have been developed in order to minimize or prevent the potentially catastrophic environmental damage that can result from an oil spill in a body of water.
Because oil has a lower specific weight than either fresh or salt water, it tends to float atop the water. Although oil floats in one or more large pools when the surrounding water is calm, ambient disturbances such as wind, rain, or waves cause the oil to diffuse over a much larger area of the surface of the water. Oil may also be spilled into rivers or other waterways, and may disperse quickly downstream. Thus it is critical to contain or stop the movement of the oil as quickly as possible, before it is allowed to diffuse, in order to facilitate removal.
Oil is typically contained by deploying buoyant oil containment booms, which are well known in the art. Exemplary of such oil containment booms is U.S. Pat. No. 4,781,493 (Fischer). As shown in FIG. 1, boom 10 is positively buoyant and extends both above and below the surface of the water 12 to prevent oil 14 from passing from first side 16 to second side 18 of boom 10. Float 20 is generally cylindrical, and a portion thereof extends above the surface of the water. Float 20 typically measures from 20 cm. to 46 cm. in diameter, and includes a central flotation core 21 surrounded by layers of fire resistant material 23, 25, and 27. The boom may also be covered by a polymeric outer layer 29 for aesthetic reasons. At least some of these layers are drawn together over an end of the flotation core to form a boom flap (represented in FIG. 5 by a single layer boom flap 131) at the end of the boom.
Skirt 22, which prevents oil 14 from escaping beneath float 20, extends downwardly from the bottom of the float. The skirt may measure on the order of 43 cm. to 92 cm., and thus the total height of the oil containment boom is typically from 63 cm. to 138 cm. Lower tension member 24 is weighted, and is attached to the bottom of skirt 22 to maintain boom 10 in the desired upright position. Boom 10 is generally flexible, in order to withstand the stresses applied by the surrounding water and waves, and to aid in encircling an oil spill.
Oil containment booms typically measure on the order of 3 meters to 15 meters long, and a plurality of booms are often connected together to form a string, which may measure in excess of 150 meters long. In order to construct the string, boom connectors are used to connect adjacent booms, and each boom connector preferably extends from the top of the booms to the bottom of the underwater skirt. The height of the boom connector is thus approximately equal to the height of the containment booms. An important consideration in the design and use of an oil containment boom connector is that the boom connector minimize, or preferably prevent the flow of oil through the boom connector from the surrounded area to the open water. This becomes particularly important when the contained oil is aflame because of the danger to the surroundings and to workers should the burning oil escape.
One known boom connector, sold by Minnesota Mining and Manufacturing Company of St. Paul, Minn., includes two parallel plate members which are joined in a face to face relationship. A similar connector is shown in FIG. 1.22(g) on page 36 of the 1991 World Catalog of Oil Spill Response Products, (3d ed.), by Robert Schultze Environmental Consultant, Inc., 6154 Rockburn Hill Road, Elkridge, Md. 21227. The first plate member typically has a peg or bolt located at the bottom that engages a slot on the bottom of the second, opposed plate member. A fastener is then inserted through a hole at the top of each of the plate members to secure the boom connector. Such connectors may develop gaps between the plate members, especially when large towing loads are applied, and the gaps may allow oil to leak from the surrounded area. It is therefore desirable to provide a boom connector that provides a more effective barrier to the passage of oil therethrough.
Another consideration related to the construction of interlocking connector portions is ease of assembly. Oil boom connectors are often manually interengaged while they are attached to booms that are in the water. Furthermore, darkness, cold, and the presence of oil each complicate the process of interengaging the boom connector to connect the oil booms together. Thus connections which require multiple manual manipulations are undesirable, and a quick-release feature is also preferable in order to minimize the effort required to disconnect the boom connector.
Boom connectors having small clearances between interengaging members are generally undesirable, because of the increased difficulty in aligning and engaging adjacent parts. The boom connectors shown in U.S. Pat. Nos. 4,295,756 (Blair) and 4,367,979 (Milligan) are representative of boom connectors that have cooperative connector portions, each portion having a channel portion and a securing portion. The securing portion of one connector portion is inserted in the channel portion of the other connector portion, and vice versa, to interengage the connector. The clearance between the respective channels and securing portions is small, which can make interengagement difficult. For example, oil booms may be used under arctic conditions, where ice can build up within the channels into which the securing portions are to be inserted, possibly preventing interengagement of the connector portions. Thus, in order to connect the oil booms, an operator would have to lift the end of each oil boom completely out of the water, remove the ice from the entire length of the channels, and again attempt to interengage the connector portions. Thus from the standpoint of interengaging the portions of an oil boom connector, small clearances are undesirable.
Once a string of booms has been assembled, a pair of boats each pull one end of the string across the water, which collects oil in the end of the U-shaped string, as shown in FIG. 2. Thus a boom connector must be strong enough to withstand the drag force applied by the water on the booms during towing. Once a quantity of oil has been accumulated within the area surrounded by the string of booms, there are numerous methods of collecting or disposing of the oil. For example, a surfactant may be added to the oil to disperse it, or the oil may be skimmed from the surface of the water. A relatively recent innovation involves burning the oil as it floats on the surface of the water. Under suitable circumstances, 95-98% of the oil can be burned away, after which the residue may be collected from the surface of the water. In order to begin and to sustain an oil fire atop a body of water, the oil must be greater than 1 millimeter thick, and preferably about 2.5 millimeters thick. In practice, the best way to collect the oil, and thus to sustain the fire is to tow a string of oil containment booms through an area where oil has settled on the water. As the oil collects against the U-shaped end of the string it is set aflame, and the continued addition of oil fuels the fire.
When oil is burned, the temperatures are typically in the range of 650.degree.-865.degree. C., and may reach 1100.degree. C. Some boom connectors are inadequate for use with oil burning, because at least some of the materials of which they are made, such as aluminum, deteriorate at temperatures well below that of burning oil. In some cases, the boom connector melts down to the surface of the water, which allows oil to wash over the top of the boom connector and escape the surrounded area. The oil boom connectors presented in U.S. Pat. Nos. 4,295,756 (Blair) and U.S. Pat. No. 4,367,979 (Milligan) are not directed to an oil boom connector for use in an oil burning environment, and in fact are preferably formed of extruded aluminum, which would begin to melt at approximately 425.degree.-600.degree. C. Oil burning as a method of disposal has thus been less effective because of the absence of a boom connector that could withstand high temperatures while maintaining an effective barrier to the leakage of oil. Furthermore, many known boom connectors were incapable of being reused, because the heat of an oil fire tended to render them inoperable.
The present invention therefore provides an oil containment boom connector that acts as an effective barrier to impede the escape of oil from a surrounded area, even when subjected to the elevated temperatures associated with burning oil. Additionally, the boom connector of the present invention is easy to assemble under adverse ambient conditions.